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Craniofacial dysmorphogenesis in fetally irradiated nonhuman primates: implications for the neurodevelopmental hypothesis of schizophrenia
Craniofacial Dysmorphogenesis in Fetally Irradiated Nonhuman Primates: Implications for the Neurodevelopmental Hypothesis of Schizophrenia Douglas L. Gelowitz, Pasko Rakic, Patricia S. Goldman-Rakic, and Lynn D. Selemon Background: Craniofacial abnormalities arising from gestational disturbances have been documented in some schizophrenic patients. Reduction of thalamic neurons, a key feature of the neuropathology of schizophrenia, could also have a prenatal origin via disruption of thalamic neurogenesis. This study investigates whether craniofacial dysmorphology and thalamic neuron loss might be associated manifestations of a disruption in embryonic development. Methods: Thalamic neurons were deleted by exposing fetal macaques to x-rays during thalamic genesis (E33– 42). Another group of macaques was irradiated after thalamic genesis (E70 – 81). Body, head, and facial measurements were obtained from the early irradiated (EX), late irradiated (LX), and control animals at adulthood. Results: Head width, distance between outer eye edges, and ear width were smaller in EX macaques compared with control animals. The LX macaques exhibited only reduced ear width compared with control animals. Conclusions: These findings indicate that certain features of thalamic neuropathology and craniofacial dysmorphogenesis observed in schizophrenic patients may have a common etiology. Biol Psychiatry 2002;52: 716 –720 © 2002 Society of Biological Psychiatry Key Words: Macaque monkey, x-irradiation, neurogenesis, thalamus, gestation, craniofacial
Introduction
T
he neurodevelopmental hypothesis of schizophrenia states that schizophrenia is often associated with early brain abnormalities that become unmasked by later developmental events occurring during adolescence or early adulthood (Marenco and Weinberger 2000; Weinberger From the Department of Neurobiology, Yale University School of Medicine, New Haven, Connecticut. Address reprint requests to Douglas L. Gelowitz, Ph.D., Yale University School of Medicine, Department of Neurobiology, 333 Cedar Street, SHM B408, New Haven CT 06510. Received October 15, 2001; revised February 1, 2002; accepted February 10, 2002.
© 2002 Society of Biological Psychiatry
1986). Recent anthropometric findings documenting multiple anomalies of the craniofacial region in schizophrenic patients are consistent with this hypothesis because craniofacial dysmorphology is a hallmark of disturbed early prenatal development (Lane et al l997; Waddington et al l999a, 1999b). Craniofacial abnormalities of the frontonasal–maxillary juncture have also been observed in schizophrenic probands and their relatives (Deutsch et al 2000), and McNeil et al (2000) reported that schizophrenic patients are more likely than normal subjects to have minor congenital physical anomalies such as reduced head circumference. In ongoing nonhuman primate studies designed to model thalamic neuronal loss in schizophrenic patients, we noted craniofacial abnormalities in fetally irradiated monkeys. The purpose of this study was to determine whether the observed craniofacial dysmorphology could be verified quantitatively and whether craniofacial abnormalities similar to those observed in schizophrenic patients arise during the time of thalamogenesis. Analysis of the data indicated that animals irradiated during the time of thalamogenesis exhibited narrowing of the head and of the distance between the outer eye edges, which are dysmorphologies similar to those observed in schizophrenic patients. Furthermore, animals irradiated during thalamogenesis, or at a later gestational time point, had smaller than normal ear widths, an anomaly common to a number of developmental disorders including mental retardation.
Methods and Materials Subjects Nine adult rhesus monkeys (Macaca mulatta) were examined in this study. The subjects were divided among three groups: Early irradiated (EX), late irradiated (LX), and control animals (CON).
Irradiation Procedure Time of irradiation and doses of x-rays administered to each animal are listed in Table 1. Pregnant monkeys were anesthetized 0006-3223/02/$22.00 PII S0006-3223(02)01380-X
Craniofacial Dysmorphogenesis and Schizophrenia
BIOL PSYCHIATRY 2002;52:716 –720
717
Table 1. Irradiation Schedule and Dose Distribution Animal ID
Sex
DOB
Group
PIP OBO ALA
M M F
9/17/91 9/17/91 4/04/91
LX LX LX
NELEN ROTOR NAN Seinfeld WESTPORT RIPLEY
M M F M M F
2/02/95 1/05/95 5/18/93 9/27/95 7/22/91 4/01/91
EX EX EX CON CON CON
Irradiation Time: embryonic day (E) irradiation dose [cGy]
Total dose cGy
E73[100], E74[100], E75[100] E73[100], E74[100], E75[100] E70[100], E72[100], E75[100] E77[100], E79[100], E81[100] E33[50], E35[50], E36[50], E37[50] E33[25], E35[50], E37[50], E41[50] E35[50], E37[50], E39[50], E42[50] No irradiation No irradiation No irradiation
300 300 600 200 175 200 000 000 000
LX, late irradiated; EX, early irradiated; CON, control; M, male; F, female.
with ketamine (5–10 mg/kg) followed by intramuscular injection of atropine (.02 mg/kg). The head of the fetus was localized, and the depth of the cranium from the abdominal surface was determined by ultrasound. X-irradiation was performed with a 250-kV, 15-mA Stabilipan x-ray tube with a Thoeraus II filter located 50 cm from the abdominal wall of the mother. The beam area was adjusted to 5 ⫻ 5 cm. The dose varied from 175 cGY to 600 cGY, and the number of exposures varied from three to six (Table 1). The exposure time was determined according to the depth of the fetal head, and the irradiation dose was calculated from a chart prepared by the Yale University School of Medicine Radiation Therapy Department (for details, see Algan and Rakic 1997). Following irradiation, the status of the fetus was monitored by ultrasound every 2 weeks during the remainder of gestation. Animals were delivered at term (E165) by Cesarean section and were housed in the Yale colony until the time of dysmorphic assessment.
Dysmorphic Assessment Procedure Assessment of stature and craniofacial structure was performed under ketamine (5–10 mg/kg) anesthesia that had been administered for routine tuberculosis testing. Body, head, and facial measurements were performed using a standard, flexible, fiberglass tape measure and a stainless steel dial caliper. The following measurements were taken on each subject: weight, height, head circumference, middle head width, outer eye distance, left and right eye socket heights, base of nose width, ear height, and ear width (Figure 1). The total dysmorphic assessment time for each monkey was approximately 20 min and was loosely based on the information in Anthropometry of the Head and Face (Farkas 1994). All assessments were conducted when subjects were mature adults within a 1-month period of time between January 21 and February 22, 2001. Although the ages of subjects somewhat varied, age was not a confounding factor because all subjects were fully mature at the time of assessment, and head growth is quite insignificant in mature rhesus monkeys (Hartman and Straus 1933). A priori, planned comparisons of each of the irradiated monkey groups in comparison to the controls (EX vs. CON; LX vs. CON) were performed using the Mann–Whitney U score. The Mann–Whitney U is a nonparametric statistical test that provides excellent power when dealing
with small, nonnormally distributed data, as was the case here. The significance level was set at p ⬍ .05 (two-tailed).
Results In EX monkeys, mean values for all 10 measurements tended to be lower than control subjects, but only three— head width, distance between outer eye edges, and ear width—reached statistical significance (Table 2). In contrast, just 6 of the 10 measurements in LX monkeys were lower than control monkeys and only one, ear width, was significantly reduced (Table 2). Interestingly, 9 out of 10 measurements tended to be lower in the EX group relative to the LX animals, although differences between these groups were not analyzed statistically. A scatter plot of all the data points for statistically significant craniofacial measurements shows complete nonoverlap of measurements in the EX and CON monkeys (Figure 2).
Discussion This study provides evidence for an association of two abnormalities caused by x-irradiation that are similar to those described in schizophrenic patients: thalamic neuro-
Figure 1. Frontal (left) and lateral (right) photos of a control monkey indicating areas where significant differences were obtained. A, head width; B, distance between outer eye edges; C, ear width.
718
D.L. Gelowitz et al
BIOL PSYCHIATRY 2002;52:716 –720
Table 2. Average Body, Head, and Facial Measurements Area measured Weight (kg) Height (cm) Head circumference (cm) Head/skull width (cm) Distance between outer eye edges (cm) Left eye socket height (cm) Right eye socket height (cm) Width at base of nose (cm) Ear height (cm) Ear width (cm) a b
EX
⫾b
LX
⫾
CON
⫾
8.58 88.95 30.10 8.06a 4.59a 1.97 1.93 1.45 4.31 a 2.28
1.56 11.62 2.47 .27 .12 .28 .30 .33 .44 .17
10.56 95.47 31.24 9.20 5.31 2.24 2.21 1.64 4.59 2.26a
2.28 10.10 3.18 .86 .38 .21 .22 .12 .37 .32
9.57 94.91 32.67 9.25 5.14 2.29 2.25 1.83 4.37 3.07
.62 1.92 1.53 .45 .27 .10 .14 .39 .39 .50
Statistically significant from control means. ⫾ standard deviation.
nal reduction and craniofacial abnormalities. Both of these abnormalities can arise as a consequence of a single perturbation during a specific stage of gestational development. Monkeys irradiated during the period of thalamic neurogenesis (EX group) had craniofacial abnormalities that were comparable to those described in human schizophrenic patients, whereas those exposed to irradiation after completion of thalamic neurogenesis (LX group) exhibited only reduced ear width. This suggests that the early gestational period, when thalamic neurons are being generated, might be more critical for proper maturational growth of the head and facial contour. Overall, our findings are consistent with the notion that early irradiation (EX group) induces a generally smaller head size. It is perhaps not surprising that neuropathology and craniofacial dysmorphogensis are related as the brain and face develop from the same embroynic primordia and are fashioned by common forces (Wilkie and Morriss-Kay 2001). Indeed, recently it has been shown that retinoic acid (Vitamin A) from neural crest-derived mesenchyme is involved in the induction and differentiation of adjacent epithelia and that disruptions to retinoic acid signaling may account for a range of craniofacial and neural
Figure 2. Scatter plot of all data points for statistically significant craniofacial measurements. Head width, distance between outer eye edges, and ear width were smaller in early irradiated macaques (EX) compared with normal control animals (CON). Late irradiated macaques (LX) exhibited only reduced ear width in comparison with control animals.
malformations (LaMantia 1999; Schneider et al 2001). These findings suggest that craniofacial genesis and brain development are linked not only by gestational time frame, but also possibly by common signaling pathways and are consistent with the notion that retinoid dysregulation may be a factor in the etiology of schizophrenia (Goodman 1998; LaMantia 1999). In addition to schizophrenia, there are a number of other human disorders in which neurologic defects or brain malformations are associated with craniofacial abnormalities, such as Fragile X-linked mental retardation and 22q11.2 deletion or velocardiofacial syndrome (Bassett and Chow 1999; Chow et al 1999; Eliez et al 2001; Rousseau et al 1994); therefore, our findings may have some relevance to these disorders as well. Interestingly, schizophrenic patients display multiple dysmorphic features of the craniofacial region, such as an overall narrowing and elongation of the midface and lower face and extensive abnormalities of the mouth, eyes, and ears (Lane et al 1997). Particularly relevant to this study, Lane et al (1997) found significantly decreased eye fissure length and nasal width in their schizophrenic population. Deutsch et al (2000) also described dysmorphology in schizophrenic patients and their siblings along the frontonasal–maxillary junction and found an association of this defect with brain midline deviation. Considering that basic facial structure in humans and nonhuman primates differs markedly, the dysmorphic features we observed in EX monkeys were remarkably similar to those seen in schizophrenic patients, albeit not identical. The EX monkeys had decreased distances between the outer edges of their eyes and showed a trend toward decreased nasal widths, which is similar to what has been observed in schizophrenic patients. Despite the close agreement between our studies and human anthropometric studies in schizophrenic patients, the results of this study must be considered preliminary for two reasons. First, the number of animals examined was small. Second, we do not yet have detailed morphometric
Craniofacial Dysmorphogenesis and Schizophrenia
data on the loss of thalamic neurons in the monkeys examined for craniofacial abnormalities in this study; however, recent magnetic resonance imaging analysis of the irradiated adult monkeys examined in this study revealed a reduction of thalamic volume in comparison to matched control animals (Schindler et al, in press), and thalamic neuronal reduction can be expected from previous studies of infant monkeys that were irradiated during the same gestational period as the EX monkeys in this study (Algan and Rakic 1997). Our findings indicate that irradiation during fetal development in the nonhuman primate can produce comorbid neuropathology and craniofacial dysmorphology resembling that observed in schizophrenic subjects. Monkeys irradiated during the period of thalamic neurogenesis have previously been shown to exhibit elevated neuronal density in the visual and prefrontal cortices, as well as reduced numbers of thalamic neurons (Algan and Rakic 1997; unpublished observations). This study has provided quantitative evidence that monkeys irradiated during this same embryonic time frame also exhibit craniofacial anomalies. Because substantial reductions in neuronal number of the mediodorsal nucleus of the thalamus (Jones 1997; Pakkenberg 1990; Popken et al 2000; Young et al 2000), increased neuronal density in the prefrontal cortex (Selemon et al 1995, 1998), and craniofacial dysmorphogensis (Deutsch et al 2000; Lane 1997; Waddington et al 1999a, 1999b) have also been observed in schizophrenic patients, our findings provide some insight into the etiology of these pathologies and are consistent with neurodevelopmental hypothesis of schizophrenia (Marenco and Weinberger 2000; Weinberger 1986).
BIOL PSYCHIATRY 2002;52:716 –720
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Deutsch CK, Hobbs K, Price SF, Gordon-Vaugh K (2000): Skewing of the brain midline in schizophrenia. Neuroreport 11:3985–3988. Eliez S, Blasey CM, Schmitt EJ, White CD, Hu D, Reiss AL (2001): Velocardiofacial syndrome: Are structural changes in the temporal and mesial temporal regions related to schizophrenia? Am J Psychiatry 158:447–453. Farkas LG (1994): Anthropometry of the Head and Face. New York: Raven Press. Goodman AB (1998): Three independent lines of evidence suggest retinoids as causal to schizophrenia. Proc Natl Acad Sci USA 95:7240 –7244. Hartman CG, Straus WL (1933): The Anatomy of the Rhesus Monkey. Baltimore, MD: Williams and Wilkins. Jones EG (1997): Cortical development and thalamic pathology in schizophrenia. Schizophr Bull 23:483–501. LaMantia AS (1999): Forebrain induction, retinoic acid, and vulnerability to schizophrenia: Insights from molecular and genetic analysis in developing mice. Biol Psychiatry 46:19 – 30. Lane A, Kinsella A, Murphy P, Byrne M, Keenan J, Colgan K, et al (1997): The anthropometric assessment of dysmorphic features in schizophrenia as an index of its developmental origins. Psychol Med 27:1155–1164. Marenco S, Weinberger DR (2000): The neurodevelopmental hypothesis of schizophrenia: Following a trail of evidence from cradle to grave. Dev Psychopathol 12:501–527. McNeil TF, Cantor-Graae E, Ismail B (2000): Obstetric complications and congenital malformation in schizophrenia. Brain Res Brain Res Rev 31:166 –178. Pakkenberg B (1990): Pronounced reduction of total neuron number in mediodorsal thalamic nucleus and nucleus accumbens in schizophrenics. Arch Gen Psychiatry 47:1023–1028. Popken GJ, Bunney WE Jr, Potkin SG, Jones EG (2000): Subnucleus-specific loss of neurons in medial thalamus of schizophrenics. Proc Natl Acad Sci USA 97:9276 –9280.
This research was supported by Grants N514841 (PR), PRMH44886 (PGR), and MH59329 (LDS) from the National Institutes of Health. The authors thank Stacy Castner, Ph.D., Heather Findlay and Peter Vosler for their technical assistance during the dysmorphic assessments of the nonhuman primates and Daniel Mathalon, M.D., Ph.D., for statistical consultation.
References Algan O, Rakic P (1997): Radiation-induced, lamina-specific deletion of neurons in the primate visual cortex. J Comp Neurol 12:335–352. Bassett AS, Chow EW (1999): 22q11 deletion syndrome: A genetic subtype of schizophrenia. Biol Psychiatry 46:882– 891. Chow EW, Mikulis DJ, Zipursky RB, Scutt LE, Weksberg R, Bassett AS (1999): Qualitative MRI findings in adults with 22q11 deletion syndrome and schizophrenia. Biol Psychiatry 46:1436 –1442.
Rousseau F, Heitz D, Tarleton J, MacPherson J, Malmgren H, Dahl N, et al (1994): A multicenter study on genotypephenotype correlations in the fragile X syndrome, using direct diagnosis with probe StB12.3: The first 2,253 cases. Am J Hum Genet 3:225–237. Schindler M, Wang L, Selemon LD, Goldman-Rakic PS, Rakic P, Csernansky JG (in press): Abnormalities of thalamic volume and shape detected in fetally-irradiated rhesus monkeys with high dimensional brain mapping. Schizophr Res. Schneider RA, Hu D, Rubenstein JL, Maden M, Helms JA (2001): Local retinoid signaling coordinates forebrain and facial morphogenesis by maintaining FGF8 and SHH. Development 128:2755–2767. Selemon LD, Rajkowska G, Goldman-Rakic PS (1995): normally high neuronal density in the schizophrenic tex. A morphometric analysis of prefrontal area 9 occipital area 17. Arch Gen Psychiatry 52:805– 818, cussion 819 – 820.
Abcorand dis-
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Selemon LD, Rajkowska G, Goldman-Rakic PS (1998): Elevated neuronal density in prefrontal area 46 in brains from schizophrenic patients: Application of a three-dimensional, stereologic counting method. J Comp Neurol 392:402–412. Waddington JL, Lane A, Larkin C, O’Callaghan E (1999a): The neurodevelopmental basis of schizophrenia: Clinical clues from cerebro-craniofacial dysmorphogenesis, and the roots of a lifetime trajectory of disease. Biol Psychiatry 46:31–39. Waddington JL, Lane A, Scully P, Meagher D, Quinn J, Larkin C, O’Callaghan E (1999b): Early cerebro-craniofacial dysmorphogenesis in schizophrenia: A lifetime trajectory model
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from neurodevelopmental basis to “neuroprogressive” process. J Psychiatr Res 33:477–489. Weinberger DR (1986): The pathogenesis of schizophrenia: A neurodevelopmental theory. In: HAW Nasrallah, DR Weinberger, editors. The Neurology of Schizophrenia. Amsterdam: Elsevier, pp 397– 406. Wilkie AO, Morriss-Kay GM (2001): Genetics of craniofacial development and malformation. Nat Rev Genet 2:458 –468. Young KA, Manaye KF, Liang C, Hicks PB, German DC (2000): Reduced number of mediodorsal and anterior thalamic neurons in schizophrenia. Biol Psychiatry 47:944 –953.
Introduction
T
he neurodevelopmental hypothesis of schizophrenia states that schizophrenia is often associated with early brain abnormalities that become unmasked by later developmental events occurring during adolescence or early adulthood (Marenco and Weinberger 2000; Weinberger From the Department of Neurobiology, Yale University School of Medicine, New Haven, Connecticut. Address reprint requests to Douglas L. Gelowitz, Ph.D., Yale University School of Medicine, Department of Neurobiology, 333 Cedar Street, SHM B408, New Haven CT 06510. Received October 15, 2001; revised February 1, 2002; accepted February 10, 2002.
© 2002 Society of Biological Psychiatry
1986). Recent anthropometric findings documenting multiple anomalies of the craniofacial region in schizophrenic patients are consistent with this hypothesis because craniofacial dysmorphology is a hallmark of disturbed early prenatal development (Lane et al l997; Waddington et al l999a, 1999b). Craniofacial abnormalities of the frontonasal–maxillary juncture have also been observed in schizophrenic probands and their relatives (Deutsch et al 2000), and McNeil et al (2000) reported that schizophrenic patients are more likely than normal subjects to have minor congenital physical anomalies such as reduced head circumference. In ongoing nonhuman primate studies designed to model thalamic neuronal loss in schizophrenic patients, we noted craniofacial abnormalities in fetally irradiated monkeys. The purpose of this study was to determine whether the observed craniofacial dysmorphology could be verified quantitatively and whether craniofacial abnormalities similar to those observed in schizophrenic patients arise during the time of thalamogenesis. Analysis of the data indicated that animals irradiated during the time of thalamogenesis exhibited narrowing of the head and of the distance between the outer eye edges, which are dysmorphologies similar to those observed in schizophrenic patients. Furthermore, animals irradiated during thalamogenesis, or at a later gestational time point, had smaller than normal ear widths, an anomaly common to a number of developmental disorders including mental retardation.
Methods and Materials Subjects Nine adult rhesus monkeys (Macaca mulatta) were examined in this study. The subjects were divided among three groups: Early irradiated (EX), late irradiated (LX), and control animals (CON).
Irradiation Procedure Time of irradiation and doses of x-rays administered to each animal are listed in Table 1. Pregnant monkeys were anesthetized 0006-3223/02/$22.00 PII S0006-3223(02)01380-X
Craniofacial Dysmorphogenesis and Schizophrenia
BIOL PSYCHIATRY 2002;52:716 –720
717
Table 1. Irradiation Schedule and Dose Distribution Animal ID
Sex
DOB
Group
PIP OBO ALA
M M F
9/17/91 9/17/91 4/04/91
LX LX LX
NELEN ROTOR NAN Seinfeld WESTPORT RIPLEY
M M F M M F
2/02/95 1/05/95 5/18/93 9/27/95 7/22/91 4/01/91
EX EX EX CON CON CON
Irradiation Time: embryonic day (E) irradiation dose [cGy]
Total dose cGy
E73[100], E74[100], E75[100] E73[100], E74[100], E75[100] E70[100], E72[100], E75[100] E77[100], E79[100], E81[100] E33[50], E35[50], E36[50], E37[50] E33[25], E35[50], E37[50], E41[50] E35[50], E37[50], E39[50], E42[50] No irradiation No irradiation No irradiation
300 300 600 200 175 200 000 000 000
LX, late irradiated; EX, early irradiated; CON, control; M, male; F, female.
with ketamine (5–10 mg/kg) followed by intramuscular injection of atropine (.02 mg/kg). The head of the fetus was localized, and the depth of the cranium from the abdominal surface was determined by ultrasound. X-irradiation was performed with a 250-kV, 15-mA Stabilipan x-ray tube with a Thoeraus II filter located 50 cm from the abdominal wall of the mother. The beam area was adjusted to 5 ⫻ 5 cm. The dose varied from 175 cGY to 600 cGY, and the number of exposures varied from three to six (Table 1). The exposure time was determined according to the depth of the fetal head, and the irradiation dose was calculated from a chart prepared by the Yale University School of Medicine Radiation Therapy Department (for details, see Algan and Rakic 1997). Following irradiation, the status of the fetus was monitored by ultrasound every 2 weeks during the remainder of gestation. Animals were delivered at term (E165) by Cesarean section and were housed in the Yale colony until the time of dysmorphic assessment.
Dysmorphic Assessment Procedure Assessment of stature and craniofacial structure was performed under ketamine (5–10 mg/kg) anesthesia that had been administered for routine tuberculosis testing. Body, head, and facial measurements were performed using a standard, flexible, fiberglass tape measure and a stainless steel dial caliper. The following measurements were taken on each subject: weight, height, head circumference, middle head width, outer eye distance, left and right eye socket heights, base of nose width, ear height, and ear width (Figure 1). The total dysmorphic assessment time for each monkey was approximately 20 min and was loosely based on the information in Anthropometry of the Head and Face (Farkas 1994). All assessments were conducted when subjects were mature adults within a 1-month period of time between January 21 and February 22, 2001. Although the ages of subjects somewhat varied, age was not a confounding factor because all subjects were fully mature at the time of assessment, and head growth is quite insignificant in mature rhesus monkeys (Hartman and Straus 1933). A priori, planned comparisons of each of the irradiated monkey groups in comparison to the controls (EX vs. CON; LX vs. CON) were performed using the Mann–Whitney U score. The Mann–Whitney U is a nonparametric statistical test that provides excellent power when dealing
with small, nonnormally distributed data, as was the case here. The significance level was set at p ⬍ .05 (two-tailed).
Results In EX monkeys, mean values for all 10 measurements tended to be lower than control subjects, but only three— head width, distance between outer eye edges, and ear width—reached statistical significance (Table 2). In contrast, just 6 of the 10 measurements in LX monkeys were lower than control monkeys and only one, ear width, was significantly reduced (Table 2). Interestingly, 9 out of 10 measurements tended to be lower in the EX group relative to the LX animals, although differences between these groups were not analyzed statistically. A scatter plot of all the data points for statistically significant craniofacial measurements shows complete nonoverlap of measurements in the EX and CON monkeys (Figure 2).
Discussion This study provides evidence for an association of two abnormalities caused by x-irradiation that are similar to those described in schizophrenic patients: thalamic neuro-
Figure 1. Frontal (left) and lateral (right) photos of a control monkey indicating areas where significant differences were obtained. A, head width; B, distance between outer eye edges; C, ear width.
718
D.L. Gelowitz et al
BIOL PSYCHIATRY 2002;52:716 –720
Table 2. Average Body, Head, and Facial Measurements Area measured Weight (kg) Height (cm) Head circumference (cm) Head/skull width (cm) Distance between outer eye edges (cm) Left eye socket height (cm) Right eye socket height (cm) Width at base of nose (cm) Ear height (cm) Ear width (cm) a b
EX
⫾b
LX
⫾
CON
⫾
8.58 88.95 30.10 8.06a 4.59a 1.97 1.93 1.45 4.31 a 2.28
1.56 11.62 2.47 .27 .12 .28 .30 .33 .44 .17
10.56 95.47 31.24 9.20 5.31 2.24 2.21 1.64 4.59 2.26a
2.28 10.10 3.18 .86 .38 .21 .22 .12 .37 .32
9.57 94.91 32.67 9.25 5.14 2.29 2.25 1.83 4.37 3.07
.62 1.92 1.53 .45 .27 .10 .14 .39 .39 .50
Statistically significant from control means. ⫾ standard deviation.
nal reduction and craniofacial abnormalities. Both of these abnormalities can arise as a consequence of a single perturbation during a specific stage of gestational development. Monkeys irradiated during the period of thalamic neurogenesis (EX group) had craniofacial abnormalities that were comparable to those described in human schizophrenic patients, whereas those exposed to irradiation after completion of thalamic neurogenesis (LX group) exhibited only reduced ear width. This suggests that the early gestational period, when thalamic neurons are being generated, might be more critical for proper maturational growth of the head and facial contour. Overall, our findings are consistent with the notion that early irradiation (EX group) induces a generally smaller head size. It is perhaps not surprising that neuropathology and craniofacial dysmorphogensis are related as the brain and face develop from the same embroynic primordia and are fashioned by common forces (Wilkie and Morriss-Kay 2001). Indeed, recently it has been shown that retinoic acid (Vitamin A) from neural crest-derived mesenchyme is involved in the induction and differentiation of adjacent epithelia and that disruptions to retinoic acid signaling may account for a range of craniofacial and neural
Figure 2. Scatter plot of all data points for statistically significant craniofacial measurements. Head width, distance between outer eye edges, and ear width were smaller in early irradiated macaques (EX) compared with normal control animals (CON). Late irradiated macaques (LX) exhibited only reduced ear width in comparison with control animals.
malformations (LaMantia 1999; Schneider et al 2001). These findings suggest that craniofacial genesis and brain development are linked not only by gestational time frame, but also possibly by common signaling pathways and are consistent with the notion that retinoid dysregulation may be a factor in the etiology of schizophrenia (Goodman 1998; LaMantia 1999). In addition to schizophrenia, there are a number of other human disorders in which neurologic defects or brain malformations are associated with craniofacial abnormalities, such as Fragile X-linked mental retardation and 22q11.2 deletion or velocardiofacial syndrome (Bassett and Chow 1999; Chow et al 1999; Eliez et al 2001; Rousseau et al 1994); therefore, our findings may have some relevance to these disorders as well. Interestingly, schizophrenic patients display multiple dysmorphic features of the craniofacial region, such as an overall narrowing and elongation of the midface and lower face and extensive abnormalities of the mouth, eyes, and ears (Lane et al 1997). Particularly relevant to this study, Lane et al (1997) found significantly decreased eye fissure length and nasal width in their schizophrenic population. Deutsch et al (2000) also described dysmorphology in schizophrenic patients and their siblings along the frontonasal–maxillary junction and found an association of this defect with brain midline deviation. Considering that basic facial structure in humans and nonhuman primates differs markedly, the dysmorphic features we observed in EX monkeys were remarkably similar to those seen in schizophrenic patients, albeit not identical. The EX monkeys had decreased distances between the outer edges of their eyes and showed a trend toward decreased nasal widths, which is similar to what has been observed in schizophrenic patients. Despite the close agreement between our studies and human anthropometric studies in schizophrenic patients, the results of this study must be considered preliminary for two reasons. First, the number of animals examined was small. Second, we do not yet have detailed morphometric
Craniofacial Dysmorphogenesis and Schizophrenia
data on the loss of thalamic neurons in the monkeys examined for craniofacial abnormalities in this study; however, recent magnetic resonance imaging analysis of the irradiated adult monkeys examined in this study revealed a reduction of thalamic volume in comparison to matched control animals (Schindler et al, in press), and thalamic neuronal reduction can be expected from previous studies of infant monkeys that were irradiated during the same gestational period as the EX monkeys in this study (Algan and Rakic 1997). Our findings indicate that irradiation during fetal development in the nonhuman primate can produce comorbid neuropathology and craniofacial dysmorphology resembling that observed in schizophrenic subjects. Monkeys irradiated during the period of thalamic neurogenesis have previously been shown to exhibit elevated neuronal density in the visual and prefrontal cortices, as well as reduced numbers of thalamic neurons (Algan and Rakic 1997; unpublished observations). This study has provided quantitative evidence that monkeys irradiated during this same embryonic time frame also exhibit craniofacial anomalies. Because substantial reductions in neuronal number of the mediodorsal nucleus of the thalamus (Jones 1997; Pakkenberg 1990; Popken et al 2000; Young et al 2000), increased neuronal density in the prefrontal cortex (Selemon et al 1995, 1998), and craniofacial dysmorphogensis (Deutsch et al 2000; Lane 1997; Waddington et al 1999a, 1999b) have also been observed in schizophrenic patients, our findings provide some insight into the etiology of these pathologies and are consistent with neurodevelopmental hypothesis of schizophrenia (Marenco and Weinberger 2000; Weinberger 1986).
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Deutsch CK, Hobbs K, Price SF, Gordon-Vaugh K (2000): Skewing of the brain midline in schizophrenia. Neuroreport 11:3985–3988. Eliez S, Blasey CM, Schmitt EJ, White CD, Hu D, Reiss AL (2001): Velocardiofacial syndrome: Are structural changes in the temporal and mesial temporal regions related to schizophrenia? Am J Psychiatry 158:447–453. Farkas LG (1994): Anthropometry of the Head and Face. New York: Raven Press. Goodman AB (1998): Three independent lines of evidence suggest retinoids as causal to schizophrenia. Proc Natl Acad Sci USA 95:7240 –7244. Hartman CG, Straus WL (1933): The Anatomy of the Rhesus Monkey. Baltimore, MD: Williams and Wilkins. Jones EG (1997): Cortical development and thalamic pathology in schizophrenia. Schizophr Bull 23:483–501. LaMantia AS (1999): Forebrain induction, retinoic acid, and vulnerability to schizophrenia: Insights from molecular and genetic analysis in developing mice. Biol Psychiatry 46:19 – 30. Lane A, Kinsella A, Murphy P, Byrne M, Keenan J, Colgan K, et al (1997): The anthropometric assessment of dysmorphic features in schizophrenia as an index of its developmental origins. Psychol Med 27:1155–1164. Marenco S, Weinberger DR (2000): The neurodevelopmental hypothesis of schizophrenia: Following a trail of evidence from cradle to grave. Dev Psychopathol 12:501–527. McNeil TF, Cantor-Graae E, Ismail B (2000): Obstetric complications and congenital malformation in schizophrenia. Brain Res Brain Res Rev 31:166 –178. Pakkenberg B (1990): Pronounced reduction of total neuron number in mediodorsal thalamic nucleus and nucleus accumbens in schizophrenics. Arch Gen Psychiatry 47:1023–1028. Popken GJ, Bunney WE Jr, Potkin SG, Jones EG (2000): Subnucleus-specific loss of neurons in medial thalamus of schizophrenics. Proc Natl Acad Sci USA 97:9276 –9280.
This research was supported by Grants N514841 (PR), PRMH44886 (PGR), and MH59329 (LDS) from the National Institutes of Health. The authors thank Stacy Castner, Ph.D., Heather Findlay and Peter Vosler for their technical assistance during the dysmorphic assessments of the nonhuman primates and Daniel Mathalon, M.D., Ph.D., for statistical consultation.
References Algan O, Rakic P (1997): Radiation-induced, lamina-specific deletion of neurons in the primate visual cortex. J Comp Neurol 12:335–352. Bassett AS, Chow EW (1999): 22q11 deletion syndrome: A genetic subtype of schizophrenia. Biol Psychiatry 46:882– 891. Chow EW, Mikulis DJ, Zipursky RB, Scutt LE, Weksberg R, Bassett AS (1999): Qualitative MRI findings in adults with 22q11 deletion syndrome and schizophrenia. Biol Psychiatry 46:1436 –1442.
Rousseau F, Heitz D, Tarleton J, MacPherson J, Malmgren H, Dahl N, et al (1994): A multicenter study on genotypephenotype correlations in the fragile X syndrome, using direct diagnosis with probe StB12.3: The first 2,253 cases. Am J Hum Genet 3:225–237. Schindler M, Wang L, Selemon LD, Goldman-Rakic PS, Rakic P, Csernansky JG (in press): Abnormalities of thalamic volume and shape detected in fetally-irradiated rhesus monkeys with high dimensional brain mapping. Schizophr Res. Schneider RA, Hu D, Rubenstein JL, Maden M, Helms JA (2001): Local retinoid signaling coordinates forebrain and facial morphogenesis by maintaining FGF8 and SHH. Development 128:2755–2767. Selemon LD, Rajkowska G, Goldman-Rakic PS (1995): normally high neuronal density in the schizophrenic tex. A morphometric analysis of prefrontal area 9 occipital area 17. Arch Gen Psychiatry 52:805– 818, cussion 819 – 820.
Abcorand dis-
720
BIOL PSYCHIATRY 2002;52:716 –720
Selemon LD, Rajkowska G, Goldman-Rakic PS (1998): Elevated neuronal density in prefrontal area 46 in brains from schizophrenic patients: Application of a three-dimensional, stereologic counting method. J Comp Neurol 392:402–412. Waddington JL, Lane A, Larkin C, O’Callaghan E (1999a): The neurodevelopmental basis of schizophrenia: Clinical clues from cerebro-craniofacial dysmorphogenesis, and the roots of a lifetime trajectory of disease. Biol Psychiatry 46:31–39. Waddington JL, Lane A, Scully P, Meagher D, Quinn J, Larkin C, O’Callaghan E (1999b): Early cerebro-craniofacial dysmorphogenesis in schizophrenia: A lifetime trajectory model
D.L. Gelowitz et al
from neurodevelopmental basis to “neuroprogressive” process. J Psychiatr Res 33:477–489. Weinberger DR (1986): The pathogenesis of schizophrenia: A neurodevelopmental theory. In: HAW Nasrallah, DR Weinberger, editors. The Neurology of Schizophrenia. Amsterdam: Elsevier, pp 397– 406. Wilkie AO, Morriss-Kay GM (2001): Genetics of craniofacial development and malformation. Nat Rev Genet 2:458 –468. Young KA, Manaye KF, Liang C, Hicks PB, German DC (2000): Reduced number of mediodorsal and anterior thalamic neurons in schizophrenia. Biol Psychiatry 47:944 –953.